Force feed cuvette



A ril 19, 1966 G. F CLIFFORD, JR 3,246,559

FORCE FEED CUVETTE Filed Dec. 26, 1961 INVENTOR. few/ye F fl/fford, J/I

United States Patent 3,246,559 FORCE FEED CUVETTE George F. Clilford, Jr., Menlo Park, Califl, assignor to Beckman Instruments, Inc., a corporation of California Filed Dec. 26, 1961, Ser. No. 161,793 7 Claims. (Cl. 88-14) This invention relates to fluid sample analyzing apparatus and more particularly to a cuvette assembly for such apparatus wherein small samples of fluid are introduced into the cuvette for optical analysis.

In the optical analysis of fluids as by a colorimeter, it was originally the practice to collect fluid samples for analysis in test tubes and then to place each test tube into the colorimeter and take readings thereon through the test tube. This approach had the disadvantage of introducing errors in the readings based upon variations in the glass of each particular test tube used.

Subsequently, to eliminate variations based on the test tubes used, an alternative apparatus was developed in which a single fixed or permanent test tube, referred to as a cuvette was incorporated in the apparatus, and the liquid samples to be analyzed were successively placed into the cuvette and then removed. One type of such apparatus is filled from the top of the cuvette and the liquid sample removed from the bottom via an opening connected to a tube. The tube is arranged to be subjected to a vacuum to remove the sample. The cuvette is cleaned between successive samples by pouring a washing solution such as distilled water, into it followed by application of a drying agent such as acetone. This procedure cleans the test tube for the next sample thereby removing all residue from the tube which might aifect readings on the following sample.

The present invention contemplates a cuvette assembly wherein fluids are force fedinto the permanent test tube or cuvette and sucked therefrom along a common channel, and which is constructed to be bodily inserted momentarily into a eolorimeter for readings to be taken on the sample in the cuvette.

Therefore, it is an object of the invention to provide an improved cuvette assembly designed for momentary insertion into optical analyzing apparatus, such as a colorifrneter, and provided with simple means for forcing fluids into the cuvette and withdrawing them therefrom.

In analyzing very small fluid volumes, the presence of bubbles in the fluid is objectionable. According to the present invention, fluid samples can beeasily forced into the cuvette without introducing bubbles into the sample, while using little or no particular skill. However, when the cuvette is to be washed out, there is little concern with regard to the formation of bubbles, and accordingly, the cuvette may be cleaned by manipulating the pump means associated therewith.

According to the present invention, there is also pro vided pump means for quickly washing out the cuvette after each sample. 1

Accordingly, it is another object of the present invention to provide a cuvette assembly wherein fluid can be either pumped into the cuvette or forcev fed thereto.

These and other objects of the invention will be pointed out in the following description and claims and illus trated in the accompanying drawings which disclose, by way of example, the principle of the invention and the best mode which has been contemplated of applying that principle.

In the drawings: a

FIGURE 1 is an elevation View partially in section looking in the direction of a light path through the cuvette assembly;

FIGURE 2 is an elevation view in section taken along 3,246,559 Patented Apr. 19, 1966 the line 2-2 of FIGURE 1 and omitting for clarity the nozzle assembly 60;

FIGURE 3 is a plan view in section taken along the line 33 of FIGURE 1 with a phantom outline showing a part of the top of the apparatus; and

FIGURE 4 is a perspective view showing the construction of a permanent test tube or cuvette together with a plug therebeneath.

Referring to the drawings and particularly to FIG- URE 1, the cuvette assembly 10 comprises a generally cylindrical holder 11 capped by a head member 12. The lower surface of head member 12 is counter-bored slightly to provide a seat 13 into which the top of holder 11 fits. Holder 11 and head member 12 are secured together by a screw 15 shown in FIGURE 2. Holder 11 is provided with an eccentrically disposed bore 16 as is head member 12 at 17, bores 16 and 17 being aligned to comprise a single cylindrical bore for receiving a cuvette 25. The lower end of bore 16 narrows down and is beveled to provide a seat 19 to receive a sealing plug 20, as best shown in FIGURE 4. Plug 20 is of a suitable material having a very slight resilience such as that sold under the registered trademark Teflon by the E. I. du Pont Corporation and which is described by the Handbook of Material Trade Names, Zimmerman and Lavine, 1953 edition, p. 558, as a plastic consisting of a tetrafiuoroethylene polymer. A hole 22 drilled axially of plug 20 receives one end of a capillary tube 23 which is frictionally held therein. A permanent test tube or cuvette 25 having a flat-sided necked down portion 26 of predetermined volume for analyzing a fluid sample therein slips into bore 16. Portion 26 is open at the bottom and rests on top of plug 20, thereby sealing the bottom except for hole 22. Cuvette 25 is firmly seated against the upper surface of plug 20 by downward pressure applied from a narrow ridge 27 formed on the bottom of a retaining ring member 28 threadedly received in the top of head member 12.

Holder 11 is further provided with a bored hole 29' which intersects bore 16 at right angles thereto. The necked-down portion 26 of cuvette 25 is oriented or turned, as best shown in FIGURE 3, so as to line up edgewise to hole 29', i.e., with the flat sides of portion 26 parallel to bored hole 29 to dispose portion 26 along a light path 31 of suitable opticalanalyzing apparatus such as a colorimeter, not shown. Such apparatus could include a photocell and light source for measuring the opacity, for example, of a fluid sample in portion 26. Transversely disposed across light path 31 is a filter holder 32 of opaque material having a vertical slot 33 therein located in light path 311. Holder 3-2 further includes a pair of retaining lips 34' for holding an optical filter therein. A portion 35 of holder 11 is cut away to provide a flat surface to which filter holder 32 can be secured as by screws 36 extending through a pair of cars 37 formed on diagonally opposite corners of holder 32 (only one of which is shown in FIG- URE 2). The side of holder 11 opposite cut away portion 35 is also cut away as at 39.

A mechanical plunger assembly 40 for cleaning and flushing cuvette 25, for example of plastic material, is provided centrally of retaining ring member 28 and slips through a drilled hole 41' therein. Assembly 40 is removable as a unit from hole 41 and is merely frictionally inserted into it. Assembly 40 comprises a sleeve 43 having a drilled hole 44 axially therethrough. The upper extent 44w of hole 44 is of slightly larger diameter in an enlarged cylindrically shaped portion 51 to provide a shoulder 52 directly therebeneath. As thus arranged, spring 47 is disposed between shoulder 52 on stem 50 and shoulder 46 Within sleeve 43 so as to provide a biasing force acting upwardly on stem 50. Stem 50 is coaxially bored to provide a filling hole 54 somewhat flared out funnel-like at its upper end.

In its assembled condition, with retaining ring 28 screwed down to hold cuvette 25 firmly in contact with plug 20, the plunger assembly 40 can be slipped into hole 41 until an exterior shoulder portion 55 on sleeve 43 contacts the upper surface of retaining ring 28. In this condition, piston 48 extends into the open upper end of cuvette 25 as does a reduced portion 56 of the lower end of sleeve 43. Fluid washing or flushing material can therefore be deposited or introduced directly into cuvette 25 via hole 54. Subsequently, pumping downwardly on stem 50 while covering hole 54 serves to force the washing solution out of cuvette 25 via capillary tube 23.

As shown in FIGURE 2, capillary tube 23 extends part way up into hole 22 in plug 20 and is disposed across the bottom of holder 11 until it bends upwardly to extend into a vertical capillary hole 58 shown best in FIGURE 3. As tube 23 leaves the upper end of capillary hole 58, it passes into a slot 59 cut radially into head member 12. A nozzle assembly 66, shown best in FIGURE 1 and omitted substantially from FIGURE 2 for purposes of clarity, is threadedly' engaged into the side of head member 12.

Nozzle assembly 60 includes a rear abutment portion 62 of substantially square construction formed with a vent hole 63. A long finger-like member 64 is formed integrally with abutment portion 62 and includes an enlarged end 65 dimensioned to snugly receive a test tube 70. Finger 64 is bored axially to provide an opening 66 which extends along finger 64 and into abutment 62 until vent 63 has been reached, thereby by-passing enlarged portion 65. Beyond this point, bore 66 narrows down as at 67 so as to snugly fit capillary tube 23. Finally, abutment port-ion 62 isformed with a threaded boss portion 68 which can be screwed into a coacting threaded hole 69. As shown in FIGURE 1, capillary tube 23 preferably extends out beyond the end of finger 64.

As thus arranged, the enlarged portion 65 can be slipped into test tube 70 and as finger 64 moves further into it, air will escape via the space between capillary tube 23 and bore opening 66 and vent 63. Hwever, by covering vent 63, fluid in test tube 70 will be pressurized so as to be driven into capillary tube 23, thereby force feeding the fluid into the open lower end of cuvette 25. By retaining vent 63 covered, as by using the middle finger or forefinger, any attempt to pull test tube 70 from finger 64 will suck the fluid sample from cuvette 25.

Finally, as best shown in FIGURE 3, an alignment detent 72 extending vertically up the side of holder 11 is provided to coact with an alignment member 73 shown in phantom lines in FIGURE 3 incorporated into an optical analyzing apparatus such as a colorimeter thereby orienting light path 31 properly disposed with respect to the orientation of cuvette 25. In this fashion, assembly '10 can be'mom'entarily inserted easily into such an optical analyzing apparatus while being removable for handling and loading with a fluid sample or flushing material as the case may be.

4 Operation between the bottom of cuvette 25 and the upper surface of plug 20.

A capillary tube of suitable length is next inserted into the vertical hole 58 in holder 11 upwardly therethrough until the upper end of capillary tube 23 extends into slot 59 where it can be pulled from its upper end. The bottom end of tube 23 is bent under holder 11 and inserted up into hole 22 in plug 20 as desired to effect a firm hold thereon. Before attaching nozzle assembly 60 to head member 12, the upper end of tube 23 isinserted through the narrow portion 67 of bore opening 66 until the upper end of capillary tube 23 extends out beyond the end of finger 64. As thus arranged, capillary tube 23 provides a single continuous channel extending from beyond the end of finger 64 at one end and an opening into the bottom of cuvette 25 at the other. Boss 68 can then be screwed into the threaded hole 69 in head member 12.

In order to facilitate the insertion of the lower end of capillary tube 23 into the bottom of plug 20, a slot 74 is cut in the bottom of holder 11.

Finally, the removable plunger assembly 40 is easily assembled by dropping spring 47 into the drilled hole 44a and inserting the stem 50 downwardly through the convolutions thereof. The lower end of stem 50 can then receive piston 48 to retain stem 50 within sleeve 43. Assembly 49 is then merely slip fitted into hole 41 and down into the upper end of cuvette 25.

From the foregoing, it will be apparent that the structure of the cuvette assembly 10 is easily disassembled for cleaning, substitution of parts, or otherwise.

To analyze a fluid sample, finger 64 is inserted into a test tube 70 until capillary tube 23 extends a limited distance into the fluid sample therein. From there on, hole 63 is covered and finger 64 is forced further into test tube 70, thereby applying pressure against the upper surface of the fluid sample. Fluid in test tube '70 escapes via capillary tube 23 into the bottom of cuvette 25 until a suificient quantity is introduced therein to provide an appropriate sample.

Cuvette assembly 10 i then momentarily placed into a colorimeter in registration with light path 31 by means of detent 72 coacting with any suitable alignment portion 73 of the colorimeter. After the sample has been analyzed, cuvette assembly 10 can be withdrawn from the colorimeter and test tube 70 pulled slowly from the end of finger 64 while vent 63 remains covered. As the interior volume of test tube 70 is increased, atmospheric pressure acting upon the fluid sample in cuvette 25 forces the sample out of cuvette 25 and back into test tube 70.

Subsequent to withdrawing the sample from cuvette 25 and in order not to contaminate the next subsequent sample, a washing solution, for example, of distilled water, can be poured directly via filling hole 54 into cuvette 25 followed by a downward push applied to piston 48 while covering the top of hole 54. As stem 50 moves upwardly under the action of spring 47, hole 54 can be uncovered if desired, although whether or not it is covered or uncovered, air will enter cuvette 25 either by tube 23 or hole 54. It is possible of course to manipulate piston 48 and use it as a pump by inserting the end of finger 64 into the washing solution. It has been found that after the washing solution has been substantially expelled from cuvette 25, it is desirableto introduce a drying agent such as acetone to the cuvette 20 so as to remove the last traces of the washing solution. This, of course, can be done directly via filling hole 54.

It will be apparent that a sample can be slowly and controllably forced into the bottom of cuvette 25 without introducing bubbles and without danger of losing any of the sample material. Furthermore, it has been found that a feature of the present invention is that once the flow has commenced between test tube 70 and cuvette 25, vent 63 can be uncovered, thereby initiating a siphoning of the fluid from test tube 70 providing the advantage of extracting the very last drop of fluid in the test tube,

While there has been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. For example, omission of vent 63 and opening 66 would cause only a limited amount of air to be trapped in the capillary tube 23 which might prove unobjectionable under certain conditions. Accordingly, it is entirely within the scope of this invention to form the capillary tube integrally molded to the plug 20 at one end and finger 65 at the other. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

I claim:

1. A cuvette assembly for insertion into optical analyzing apparatus having a light path therein, said cuvette assembly comprising a transparent cuvette chamber, body means supporting said chamber with a portion of same oriented to be inserted into said light path, a tube leading into the bottom interior of said cuvette at one end and open to atmosphere at the other, means supporting said tube at the end open to atmosphere, said tube support means being supported by said body means, said tube support means including a finger-like member adapted for insertion into a test tube, a longitudinal bore in said finger-like member, said tube being disposed in said bore, a portion of said bore being dimensioned to hold said tube, and said finger-like member having an exterior portion dimensioned and adapted to snugly receive a test tube to provide a plunger action therewith.

2. A cuvette assembly for insertion into optical analyzing apparatus having a light path therein, said cuvette assembly comprising a cuvette chamber open to atmosphere, said cuvette chamber having a transparent analyzing region therein adapted to be inserted into said light path, body means supporting said cuvette with said analyzing region thereof in position to be interposed into said light path, said body means including means for replaceably registering said analyzing region with respect to said light path, a tube leading into the bottom interior of said cuvette at one end and open to atmosphere at the other, means supporting said tube at the end open to atmosphere, said tube support means being supported by said body means, said tube support means including a finger-likemember adapted for insertion into a test tube, a longitudinal bore in said finger-like member, said tube being disposed in said bore, a portion of said bore being dimensioned to hold said tube, the exterior of said finger-like member having an enlarged plunger portion dimensioned and adapted to snugly receive a test tube thereon to force feed fluid into said cuvette chamber via said bore.

3. The invention according to claim 2 wherein said tube support means includes a distal end adapted to be inserted into a test tube, and further wherein said tube protrudes out beyond said distal end thereby being adapted to extend into constricted portions of test tubes forced upon said finger-like member.

4. The invention according to claim 2 wherein said finger-like member includes an air relief passage disposed to bypass said plunger portion, one end of said passage terminating in an opening adapted to be covered by a finger of one holding the assembly.

5. The invention according to claim 2 further including mechanical pumping means, said pumping means including a piston disposed to move between limits axially within said cuvette chamber, a piston rod coupled to said piston and terminating exteriorly of said cuvette assembly, biasing means urging said piston toward one of said limits, and means defining said limit whereby manipulation of said piston rod alternately applies pressure and partial vacuum to said chamber.

6. The invention according to claim 5 wherein said piston rod is provided with an axial opening therethrough serving to permit the introduction of fluids directly into said cuvette chamber via said opening.

7. The invention according to claim 5 wherein said pumping means is removable as a unit from the balance of said cuvette assembly.

References Cited by the Examiner UNITED STATES PATENTS 890,018 6/1908 Burt. 2,660,342 11/1953 Ruf 73425.6 X 2,940,448 6/1960 Furlong 128276 3,053,138 9/1962 Sanz 88-l4 DAVID H. RUBIN, Primary Examiner.

IEWELL H. PEDERSEN, Examiner.

THOMAS L. HUDSON, Assistant Examiner. 

1. A CUVETTE ASSEMBLY FOR INSERTION INTO OPTICAL ANALYZING APPARATUS HAVING A LIGHT PATH THEREIN, SAID CUVETTE ASSEMBLY COMPRISING A TRANSPARENT CUVETTE CHAMBER, BODY MEANS SUPPORTING SAID CHAMBER WITH A PORTION OF SAME ORIENTED TO BE INSERTED INTO SAID LIGHT PATH, A TUBE LEADING INTO THE BOTTOM INTERIOR OF SAID CUVETTE AT ONE END AND OPEN TO ATMOSPHERE AT THE OTHER, MEANS SUPPORTING SAID TUBE AT THE END OPEN TO ATMOSPHERE, SAID TUBE SUPPORT MEANS BEING SUPPORTED BY SAID BODY MEANS, SAID TUBE SUPPORT MEANS INCLUDING A FINGER-LIKE MEMBER ADAPTED FOR INSERTION INTO A TEST TUBE, A LONGITUDINAL BORE IN SAID 